1. Field of the Invention
The present invention relates to an original feeding apparatus for feeding originals one by one from an original stack to a predetermined reading position in the main body of a copying machine, an original reading apparatus, and an image forming apparatus provided with them. More particularly, the invention relates to an original feeding apparatus installed in an image forming apparatus with a mechanism for sliding the original feeding apparatus and an image reading portion, and constructed to be able to decrease variation in the position of the center of gravity of the image forming apparatus in the sliding operation and reduce the apparatus in size, an original reading apparatus, and an image forming apparatus provided with them.
2. Description of Related Art
As conventional digital copying machines, facsimile machines, etc., there are image forming apparatuses consisting of an image forming portion A, an image reading portion B, and an original feeding apparatus C for feeding originals one by one to the reading position in the image reading portion B and discharging each original after completion of reading onto an original discharge table, as shown in FIG. 7.
The image reading portion B shown in FIG. 7 is constructed in structure wherein scanning rails 52 are located on the left and right sides of a frame 51 and an original reading sensor 53 runs on the rails and in parallel with an original glass stand 54 to read an original set on the original glass stand 54 (in a book mode).
The original glass stand 54 is provided with a butt member 55 for setting an original P by butting the edge of the original P against it.
A reader motor 56 translationally moves the original reading sensor 53 along the scanning rails 52 by a driving portion 57, as shown in FIG. 8.
In an operation of reading originals fed from the original feeding apparatus C, the original reading sensor 53 is located at the reading position D (see FIG. 7) and the originals are fed and conveyed one by one from an original stacking tray 58 of the original feeding apparatus C to be moved in the sub-scanning direction above the reading position D whereby each original is read.
Some image forming apparatuses have a mechanism for sliding the image reading portion B relative to an outer cover and unit and relative to the image forming portion A on occasions of mounting or dismounting a process cartridge, or performing maintenance inside the apparatus for inspection and the like.
In the apparatus shown in FIG. 7, a lever 59 is pulled to enable sliding of the image reading portion B in the X-direction (to the left).
Since the original feeding apparatus C is fixed at a predetermined position of the image reading portion B, the original feeding apparatus is also slid together with the image reading portion B during the sliding operation of the image reading portion B.
However, the image reading portion B is composed of a number of components including the frame 51, the original glass stand 54, the original reading sensor 53, the driving portion for driving the original reading sensor 53 (the motor 56 and others), and so on. Further, the original feeding apparatus C is also composed similarly of a number of components including a plurality of rollers for conveying an original, a frame, a discharge tray, a driving portion, etc. As a result, the image reading portion B and the original feeding apparatus C sum up, for example, even to the weight of 2 kg or more in certain cases.
Particularly, in the case of the original feeding apparatus C, the center of gravity thereof is located on the left side, because a lot of components are positioned on the reading position D side, as shown in FIG. 7.
In the case where the sliding units have the weight as described above and the center of gravity is located on the front end side (the left side) in the sliding direction, the position of the center of gravity of the image forming apparatus varies during the sliding operation, and the image forming apparatus becomes easy to lean to the side of sliding shift.
Further, if the sliding units themselves have an ill center of gravity balance, they will be slid while leaning to the center of gravity side, resulting in failure in smooth sliding.
Since the original edge butt member 55 in the book mode is located on the left side and the reading position in the flow-reading mode is further located on the left side, as shown in FIG. 7, the butt member 55 has to be positioned on the right side of the reading portion D. This necessitates increasing the lateral width of the original glass stand 54, which will lead to a problem of inducing an increase in size of the apparatus.
Further, since the driving portion (reader motor 56) for driving the reading sensor 53 of the image reading portion B requires a space larger than the other parts in the direction along the height of the image reading portion B, the reader motor 56 projects to the side of the image forming portion A, as shown in FIG. 7. Accordingly, the image forming portion A must be cut off in the moving range of the reader motor 56 in order to allow the sliding motion of the image reading portion B. If the moving range of the reader motor 56 is large, the cut region of the image forming portion A will be large and no component can be set in that region, posing a problem of inducing an increase in size of the apparatus in the height direction.